While four-cycle gasoline engines of the type commonly used in automobiles and trucks include reservoirs which are filled with oil and pumps for distributing the oil to lubricate the operation of the engine, two-cycle engines do not include separate oil reservoirs. The lubricating oil is rather mixed with the gasoline for powering the engine. When the gasoline is carbureted into the two-cycle engine's cylinders, it also provides the necessary lubrication.
Two-cycle engines are typically employed to power relatively small, portable devices such as marine outboard engines, lawnmowers, chainsaws or the like, and these smaller engines are not filled with gasoline directly from a pump as are the four-cycle engines of automotive vehicles. Rather, they are typically filled from small containers which might hold between one and five gallons of gasoline. The containers are typically filled with gasoline directly from a pump, and the lubricating oil is provided in separate small containers of approximately one or two pint capacity. An appropriate amount of lubricating oil is added into the gasoline container, and mixed with the gasoline, before the two-cycle engine is filled with the mixture.
Not uncommonly, operators of two-cycle engines forget to mix oil with the gasoline, causing damage to the engine. Occasionally, a mixture of gasoline and lubricating oil intended for two-cycle engines will be added to four-cycle engines, which may result in improper operation of the engine, excessive smoke from the exhaust, or possibly damage to the engine.